Pressure-sensitive transfer elements and method of producing same



United States Patent 3,411,935 PRESSURE-SENSITIVE TRANSFER ELEMENTS AND METHOD OF PRODUCING SAME Hermann Winzer, Duren, Rhineland, Germany, assignor to Renker-Belipa G.m.b.H., Lendersdorf-Krauthausen,

Germany No Drawing. Filed Oct. 22, 1965, Ser. No. 502,575 19 Claims. (Cl. 11736.4)

The present invention relates to pressure-sensitive transfer elements, and to methods of producing same. More particularly, it relates to pressure-sensitive transfer elements having a layer operating the transfer of said pigment particles which are deposited in depressions of one surface of a carrier, for example, a sheet of paper.

Numerous methods of producting pressure-sensitive transfer elements have previously been proposed. For example, it has been proposed to make such elements in the form of sheets which can be used for making copies without using the conventional carbon papers. Such sheets have been prepared by coating a support with an ink layer and then with another layer which covers the ink and which contains substances which, when pressure is exerted, as by writing, are transferred together with the ink to the paper or other surface on which the copies are to be made, and adhere thereto.

In producing such pressure-sensitive transfer agents inks of conventional composition containing waxes and color pigments have been pressed in the cold state onto a suitable support, such as, for example, paper sheets, to form an ink layer, which was then subjected to subsequent heating in order to consolidate the ink. Such wax-containing carbon ink coatings have also been given a wax coating for the purpose of preventing any unintentional transfer of the transfer agent when using such transfer agents. The sharpness of the copies made with such transfer agents, however, suffers because of the wax contained in both layers, i.e. in the carbon ink layer itself and in the top coating layer. A further disadvantage in the use of such transfer agents results from the fact that usually they smear badly due to the wax content of the two layers.

Resins or rubbers have also been used for the top coatings of pressure-sensitive transfer elements of the type described above but such transfer elements likewise are subject to the disadvantages of lack of sharpness in copies produced therewith and they also cause smearing of the copies prepared therewith. These disadvantages also occur even if the mixture of the ink and wax is first applied to the support itself from the separately applied components by the use of pressure or heat. Even attempts to apply a coating of ink in powder form to the support followed by covering the ink with a protective coating of soap-like substances has not given results which were any more satisfactory.

It has now been found that When pressure-sensitive transfer elements are produced in accordance with the present invention the disadvantages inherent in the previous transfer elements of this type are overcome in that the copies prepared with applicants transfer elements show sharp contours and clearness of transferred characters. In addition, they possess excellent smear resistance and do not rub off readily and thus are well suited for storage. A comparatively large number of copies of excellent quality can be made.

3,411,935 Patented Nov. 19, 1968 "ice The pressure-sensitive transfer elements according to the invention comprise a donative surface provided with depressions into which pigment particles are deposited, said particles being enveloped by elastic binders eventually softened, and furthermore a receiving surface serving for acceptance of the writing. Between the said surfaces, preferably on the donative pigmented surface, a layer is arranged, operating the transfer of pigment particles under the writing pressure by means of its proper special adherence to the pigmented surface as well as to the receiving surface. Both the above-mentioned surfaces preferably form the top side and the back side of a carrier used as transfer element, for example, in the form of a sheet consisting of organic or inorganic material, such elements being used in the form of sets.

Especially suitable as carriers for the transfer elements are paper sheets with a thickness of 20 to 80 mu, the surfaces of such sheets not being smooth, but showing over the whole area depressions spaced about 150 mu, being of the smallest dimensions and having a depth of at least 10 to 60% of the thickness of the sheet, and their limits being determined by the surface protrusions of the support, which may be paper fibers having a breadth preferably of up to 50 mu.

Pigment particles are deposited in the depressions of the supports in a special manner so as to form the coloring material according to the present invention. In order to do this, the pigment is first ground, where necessary, to the desired degree of fineness, it being necessary that the pigment particles be smaller than the depressions of the support. The pigment particles are then dispersed in 25% (based on the weight of the pigment) of a resilient vinyl polymer dissolved in a liquid which is a nonsolvent for the pigment. When prepared in this manner each particle of pigment will be enveloped by a thin elastic coating of vinyl polymer. It is also possible to grind the pigment to the desired degree of fineness after it has been added to the binder composition. It has been found also that especially good results are obtained by mixing with the pigment a small amount of silica, preferably in colloidal form.

The pigment composition thus prepared is applied to the face of the carrier which is provided with the depressions. Any surplus of coating applied to the support is removed by a doctor blade resting directly on the surface of the support, so that after the coating is dried the amount of polymer enveloping the pigment particles will only be sufficient for filling the depressions and uncovered protruding surface parts will remain.

Preferred pigments for use in the invention are lac dyes (organic dyestuffs set on inorganic pigments). Since they are insoluble in the solvents usually used for vinyl polymers (e.g. methanol and water) the danger of the color showing through the paper or other support is avoided. even when thin papers are employed. However, other coloring materials are also suitable, as for example, phthalocyanine dyes and inorganic pigments such as ultramarine, or organic and inorganic pigment blacks.

The vinyl polymer is preferably a vinyl acetate having a medium molecular weight of about 20,00050,000. However, other vinyl copolymers may also be used, as for example, vinyl chloride/vinyl acetate (ratio: 8090 and -1()%; K-value -65), or polyvinyl alcohols containing about 12% acetyl groups.

It is important to note that the ratios of binder specified above (15-25%) are fairly critical, the use of substantially smaller quantities of vinyl polymer resulting in defective coatin-g of the pigment particles and scaling of the pigment off from the surface. The use of substantially greater quantities, however, results in too strong adhesion of the pigment particles to the support with the result that the transfer of the writing is impaired.

The inventive preparation provides suflicient adhesion of the pigment particles to the support to prevent rubbing off, or smearing of the pigment color, although permitting the removal of the pigment particles during use by the adhesive transfer layer.

The transfer layer of the present invention is applied irthe form of a gel, i.e., a double phase system consisting of a network of solid aggregates in which liquid is held.

In preparing the gel of the present invention use is made of an aliphatic carboxyl-containing hydrocarbon compound containing 25-40 carbon atoms and having an acid number of 10-160, a saponification value of from 100 to 180, and an unsaponifiable part of 5-25%. Use may also be made of polyethylenes, or mixtures thereof, having a mean molecular weight of about 1500-2000, a melting point of about 80-110 C., and a viscosity of 100-220 cps./ 140 C. The gel composition of the present invention can be prepared in various manners.

'One suitable method comprises dissolving the said hydrocarbon compound in a suitable solvent therefor, which may be a liquid hydrocarbon containing 4-12 carbon atoms, or a liquid chlorinated hydrocarbon containing 1-6 carbon atoms, at the boiling point of the solvent, and cooling the solution to l-30 C. The gel formed in this manner contains not in excess of 5% of the said hydrocarbon compound in a dissolved state and not more than of this solution included in the solid phase. Prepared as above described, the gel is solvated by the dispersion medium itself, i.e., the dispersing agent and solvating agent are identical.

A second method which can be used for the preparation of the gel comprises dispersing the said hydrocarbon compound in the molten state in water at a temperature between 75 and 98 C. in the presence of 05-30% by weight of an oil-in-water emulsifying agent and in the presence of about 10% by weight of liquid fatty alcohols containing 6-18 carbon atoms. These compounds are dispersed in the temperature range of 75-98 C. until the fatty alcohol and the hydrocarbon compound form a single phase, i.e., combined droplets. The dispersion is then cooled to 10-30 C. forming a gel of the said hydrocarbon compound, in which the fatty alcohol constitutes the solvating agent, and which gel may also contain the said hydrocarbon compound in a dissolved state. This method uses as the dispersing agent a liquid which is nonsolvent for the said hydrocarbon compound, i.e., Water. Consequently, the dispersing agent (water) and the solvating agent (liquid fatty alcohol) are not identical.

Examples of fatty alcohols to be used in the present invention are as follows:

According to a third modification, in order to produce the gel from a melt, the said hydrocarbon compound is converted to the liquid state by melting at a suitable elevated temperature in the presence of about 10% of a liquid fatty alcohol containing 6-18 carbon atoms, and subsequently cooled to a temperature of 60-90 C. This molten gel, after applying, is cooled to a temperature below the solidifying point of the melt. In such a case the fatty alcohols constitute the solvating agent. The gel is formed by melting the said solid hydrogen compound without a dispersing agent but together with the solvating agent being fatty alcohols containing 6-18 carbon atoms. In this case, no dispersing agent is used, only solvating agent being employed.

With a view to forming the transfer layer one of the hereinabove described gel preparations which all have a condition fit for the coating procedure is applied either to that face of the carrier whose depressions are filled with the enveloped pigment particles or to one surface of a receiving sheet. The thus coated carrier is cooled (in the case of applied molten gel) and carefully dried, for example, by a slightly heated air flow. In this manner is removed an excess solvent from the liquid moiety of the gel. Thus, after the drying a transfer layer in the form of an immobilized gel is obtained, which is a network of solid aggregates of used carboxyl groups containing hydrocarbon compounds, as defined hereinabove,

including a solution of said hydrocarbon compounds as liquid phase of the gel.

It should be strongly emphasized that the application of a transfer layer in the form of a solution or a melt not containing a solvated phase would not give satisfactory results, since such a solution or melt would penetrate the carrier and make transfer impossible because the necessary peculiar adhesiveness of the transfer layer according to the present invention is not efiected and all of the particles would be bound fast together and to the support.

The use of the transfer materials in the form of an immobilized gel has the advantage that the intramolecular liquidity of the gel, containing still liquid parts of the said hydrocarbon compounds, gives this peculiar adhesiveness of the transfer layer and in addition long shelf life to paper or other supports coated therewith.

The transfer layer may be applied over the pigment particles and may be connected thereto by adhesion. The transfer layer, however, may also be used as a surface preparation for the sheet receiving the writing. In this latter case also, it will bind the pigment particles transferred to it under pressure from the pigment support in a manner so as to render it resistant to smearing and rubbing off. In the manufacture of sets of sheets the sheets located below the top writing sheet may also be coated on their top sides with the transfer layer and prepared on the bottom sides with the pigment particles.

The specific examples given below are for the purpose of illustrating further the invention disclosed above. It will be understood, however, that variations from these specific examples will be obvious to one skilled in the art. Any such variation, however, which does not depart from the basic concept of the invention disclosed above is intended to come within the scope of the appended claims.

compound having mean C-atom number, of

28, an acid number of -155, a saponification number of -180 and an unsaponifiable part of 710% 7.0 Carbon tetrachloride 93.0

As the support, a paper web was used, 40 mm. in thickness, the surface of which showed depressions having 10- 60% of the thickness of the support in depth and being spaced about 1-50 mu by surface protrusions of the support. The above pigment coating was applied on this paper web by conventional means and the excess then removed by a doctor blade resting directly upon the protrusions of the paper surface, so that the depressions of the paper surface were filled while the protrusions remained uncovered. To the support bearing the pigment was then applied the above-described transfer coating preparation while in the gelatinous state. This was accomplished by heating the applicator roller and the feed bath containing the transfer coating solution to a temperature at which the said hydrocarbon compound was completely solvated, and by subsequently cooling the resulting solution until gel formation began. If required, in order to prevent any penetration of the coating into the support, the operation was speeded up by cooling by any suitable means. Any excess transfer solution was removed by a doctor blade or other suitable means. After evaporation of the excess solvent out of the coating and the coating was dry the web could then be rolled up for convenient storage.

The transfer layer thus prepared was anchored to the pigment particles of the first coating by the part of the said hydrocarbon compound remaining in a solute state. The weight of such transfer layer is approximately 1-5 grams per square meter.

Other methods of applying the transfer coating have also proven to be satisfactory, as for example, by means of spray guns. For uniform distribution and removal of excess material satisfactory results have been obtained by substituting air brushes for the doctor blades or scrapers.

In each case care must be taken, however, to ensure that the transfer preparations are kept sufiiciently thin so as to give uniform entrainment thereof on the application roller. Also, precautions must be taken, as for example, by means of mixing or stirring equipment, to avoid excessive coagulation of the solid particles.

The above preparations were applied as described in Example I.

Example HI Pigment coating: Amount in pts. by wt. Ultramarine 15.0 Silica 2.0 Polyvinyl alcohol (88% hydroxyl groups; K=

value 30) 1.5 Water 81.5 Transfer layer:

Aliphatic carboxyl-containing hydrocarbon compound having mean C-atom number of 35, an acid number of 18-25, a saponification number of 120-130 and an unsaponifiable part of 20-25% 20.0 Olein 2.5 Sperm oil 2.5 Water 75.0

A paper support 60 mu in thickness shaped like the paper described in Example I was used and coated with the above-described pigment composition as described in Example I. In this case, the transfer layer composition was prepared by melting the said hydrocarbon compound, dispersing the melt in boiling water, adding the sperm oil and olein, and further promoting the dispersion by continual stirring. The above-described transfer layer thus prepared was then applied to the support, the surplus removed by a scraper and the coated web dried by a current of hot air at a temperature a few degrees below the melting pont of the said hydrocarbon compound.

The above pigment composition was applied to a paper support in the manner described in Example I. The trans fer layer composition was then applied in the form of a solidifying melt to the paper web without using a solvent as in the preceding examples. This was effected by mixing the said hydrocarbon compound with the paraffin wax, melting in a bath with the addition of the sperm oil and subsequently cooled to approximately 15 C. above the point of solidification. The application roller used was maintained at a temperature not greater than about 10 C. above the temperature of the composition, so that at the moment of contact with the paper support the melt solidified and the particles of it were unable to penetrate into the support and were anchored superficially only by the liquid parts. The material was then cooled sufliciently to permit the applied melt to completely solidify.

The coated sheets prepared as described in Examples 'I-IV gave sharp copies when used in the customary manner and, in addition, were less subject to smearing and rubbing off than similar coated sheets prepared by previous methods using compositions containing conventional waxes and top transfer coatings.

Papers, or other supports, coated in accordance with the present invention are especially suited for use for telex rolls, bookkeeping rolls, endless forms, sets of forms for typewriters and office duplicating machines, daily summaries for banks, payroll forms, transfer forms, weight cards, weight lists, address labels, express forms with duplicate and adhesive addresses, consi-gnment notes, police reporting forms, cash-register rolls, wage lists and wage accounting forms, and for many other purposes.

What is claimed is:

1. Pressure-sensitive transfer elements for producing copies, comprising supports 20-80 mil in thickness hav ing on the surface thereof depressions 10-60% of the thickness of said support, and said depressions being spaced about 1-50 mu by protrusions of said support, pigments enveloped in 1525% of the pigment weight resilient polyvinyl polymers deposited in said depressions of said support, the size of said pigments being smaller than the said depressions, said dried pigment coating being covered with a transfer layer in amount ranging from 1 to 5 gr./m. built up by a gel formed by a network of solid aggregates of aliphatic carboxyl-containing hydrocarbon compounds containing 25-40 carbon atoms, and having an acid number of 10-160, a saponification number of 100-108, an unsaponifiable part of -25%, and a solvated fluid phase included in the network-like solid phase in an amount not exceeding 10% by weight of said hydrocarbon compounds.

2. Pressure-sensitive transfer elements for producing copies according to claim 1, wherein the support is paper sheets. i

' 3. Pressure-sensitive transfer elements for producing copies according to claim 1, wherein the pigment particles are inorganic pigments having oragnic dyestuifs deposited thereon.

4. Pressure-sensitive transfer elements for producing copies according to claim 1, wherein the pigment particles are ultramarine particles.

5. Pressure-sensitive transfer elements for producing copies according to claim 1, wherein the pigment particles are phthalocyanine particles.

6. Pressure-sensitive transfer elements for producing copies according to claim 1, wherein the pigment particles are pigment black particles.

7. Pressure-sensitive transfer elements for producing copies according to claim 1, wherein the resilient polyvinyl polymers are polyvinyl acetates having an average molecular weight of 20,000-50,000.

8. Pressure-sensitive transfer elements for producing copies according to claim 1, wherein the resilient polyvinyl polymers are polyvinyl alcohols having an acetyl content of approximately 12%.

9. Pressure-sensitive transfer elements for producing copies according to claim 1, wherein the resilient polyvinyl polymers are vinyl chloride/vinyl acetate copolymerisates containing about 80-90% vinyl chloride and 10-20% vinyl acetate and having a K-value of 40- 65.

10. Pressure-sensitive transfer elements for producing copies according to claim 1, wherein the fluid phase of the gel forming the transfer layer is a liquid aliphatic hydrocarbon containing 4-12 carbon atoms.

11. Pressure-sensitive transfer elements for producing copies according to claim 1, wherein the fluid phase of the gel forming the transfer layer is a liquid aliphatic chlorinated hydrocarbon containing l-6 carbon atoms.

12. Pressure-sensitive transfer elements for producing copies according to claim 1, wherein the fluid phase of the gel forming the transfer layer is a liquid fatty alcohol containing 6-18 carbon atoms.

13. Pressure-sensitive transfer elements for producing copies according to claim 1, wherein the solvated fluid phase of the gel forming the transfer layer contains not more than approximately 5% by weight of said solid phase forming aliphatic carboxyl-containing hydrocarbon compounds in a solute state.

14. Method for producing a pressure-sensitive transfer element for producing copies comprising applying to a paper support 20-80 mu in thickness, the surface area of which having depressions 1060% of the thickness and spaced approximately 1-50 mu by protrusions of said paper, a pigment dispersion containing pigment particles smaller in size than the depressions of said support and dispersed in a nonsolvent for said pigment and containing 15-25% by Weight, based on the pigment, of a resilient vinyl polymer, removing the excess of said pig'- ment dispersion from said paper support by a doctor blade resting directly on the surface of said paper support, whereby only the depressions therein are filled with pigment enveloped in resilient vinyl polymer and the protruding surface parts of said surface remain bare; drying said pigment coating; and applying to said dried pigment coating a transfer liquid composition produced by solving 5-30 parts by weight of aliphatic carboxyl-containing hydrocarbon compounds containing 25-40 carbon atoms, and having an acid number of 10-160, a saponification number of 100-180, an unsaponifiable part of 5-25%; in 70- 95 parts by weight of a liquid hydrocarbon containing 4-12 carbon atoms, at the boiling range of the fluid solvent,

and cooling to a temperature of 10-30 C., whereby a gel of said hydrocarbon compound is formed; after applying said transfer composition at a temperature range between 10 and 30 C., removing the surplus of said coating by means of a doctor blade, thereby obtaining a weight of the layer in the range of 1-5 mg./cm. surface area, drying the said liquid coating at a temperature a few degrees below the melting point of the said gel containing the said aliphatic carboxyl-containing hydrocarbon as a solid phase,

including not in excess of 10% by weight of solvated fluid phase, thereby forming a network of solid aggregates as a coherent layer adhering to said pigment coating.

15. The method of claim 14, wherein the transfer layer is produced with a liquid chlorinated hydrocarbon containing l-6 carbon atoms as fluid solvent.

16. The method of claim 14, wherein the transfer layer is produced by solving 5-15 parts by weight of an aliphatic carboxyl-containing hydrocarbon compound containing 25-40 carbon atoms, and having an acid number of 10- 160, a saponification number of 100-180, an unsaponifiable part of 5-25 and 5-15 parts 'by weight of a polyethylene having a mean molecular weight of 1500-2000, a melting point of 80l10 C. and a viscosity of 100-220 cps/140 C., in -95 parts by Weight of a liquid hydrocarbon containing 4-12 carbon atoms, at the boiling range of the liquid solvent, and cooling to a temperature of 10-30 C., whereby a gel of said hydrocarbon compound is formed.

17. The method of claim 14, wherein the transferlayer composition is produced by solving 5-15 parts by weight of aliphatic carboxyl-containing hydrocarbon compounds containing 25-40 carbon atoms and having an acid number of 10-160, a saponification number of 100-180, an unsaponifiable part of 5-25%, and 5-15 parts by weight of a polyethylene having a mean molecular weight of 1500- 2000, a melting point of -1l0 C. and a viscosity of 100-220 cps./ 140 C.; in 70-90 parts by weight of a liquid chlorinated hydrocarbon containing 1-6 carbon atoms, at the boiling range of the liquid solvent, and cooling to a temperature of l030 C., whereby a gel of said hydrocarbon compound is formed.

18. The method of claim 14, wherein the transfer layer composition is produced by melting an aliphatic carboxylcontaining hydrocarbon compound containing 25-40 carbon atoms, and having an acid number of 10-160, 2. saponification number of 100-180, an unsaponifiable part of 5-20%, and by adding as a dispersing agent boiling water in an amount of 4-6 times by weight as much as said liquified hydrocarbon compound, adding further an oil-in-water emulsifying agent and a liquid fatty alcohol containing 6-18 carbon atoms in an amount of not in excess of 15% by weight of the said hydrocarbon compound, and dispersing said mixture at a temperature of -100 C., until the said liquified hydrocarbon compound and said fatty alcohol form together one phase of the dispersion, and then cooling with continual stirring the mixture produced in such manner, whereby a gel of the said hydrocarbon compound is formed, coating said dried pigmerited coated support with the said gel, removing the surplus with a scraper and drying the resulting coating at a temperature a few degrees below the melting point of the said liquified hydrocarbon compound by a current of hot air, whereby a network of solid aggregates containing not in excess of 10% of solvated liquid phase, is formed as a coherent layer adhering to said pigment coating,

19. The method of claim 14, wherein the transfer layer composition is produced by melting 70-85% by weight of an aliphatic carboxyl-containing hydrocarbon compound containing 25-40 carbon atoms, and having an acid number of 10-160, a saponification number of -180, an unsaponifiable part of 5-25%; mixed with 15-25 parts by weight of a paraflin wax having a melting point of 58-65 0; adding a liquid fatty alcohol containing 6-18 carbon atoms, in an amount of not in excess of 15 by weight of the said hydrocarbon compound while continually stirring, and cooling the resulting mixture to a temperature 5-l5 C. above its melting temperature, whereby a gel of said hydrocarbon compound is formed, adding to said pigment coated support the said gel, removing the surplus of the melt from said surface by means of a scraper, and cooling said material, at least until the said applied melt becomes solidified, whereby a network of solid aggregates containing not in excess of 10% of solvated fluid phase, is formed as a coherent layer adhering to said pigment coating.

References Cited UNITED STATES PATENTS Strauss 1l7-36.3

Mino l1736.3

Breidthardt 1l736.3 Schutzmer et al 17736.3

Strauss 1l7-3 6.3

Ermst 117--3 6.3

10 MURRAY KATZ, Primary Examiner. 

1. PRESSURE-SENSITIVE TRANSFER ELEMENTS FOR PRODUCING COPIES, COMPRISING SUPPORTS 20-80 MU IN THICKNESS HAVING ON THE SURFACE THEREOF DEPRESSIONS 10-60% OF THE THICKNESS OF SAID SUPPORT, AND SAID DEPRESSIONS BEING SPACED ABOUT 1-50 MU BY PROTRUSIONS OF SAID SUPPORT, PIGMENTS ENVELOPED IN 15-25% OF THE PIGMENT WEIGHT RESILIENT POLYVINYL POLYMERS DEPOSITED IN SAID DEPRESIONS OF SAID SUPPORT, THE SIZE OF SAID PIGMENTS BEING SMALLER THAN THE SAID DEPRESSIONS, SAID DRIED PIGMENT COATING BEING COVERED WITH A TRANSFER LAYER IN AMOUNT RANGING FROM 1 TO 5 GR./M.2 BUILT UP BY A GEL FORMED BY A NETWORK OF SOLID AGGREGATES OF ALIPHATIC CARBOXYL-CONTAINING HYDROCARBON COMPOUNDS CONTAINING 25-40 CARBON ATOMS, AND HAVING AN ACID NUMBER OF 10-160, A SAPONIFICATION NUMBER OF 100-108, AN UNSAPONIFIABLE PART OF 5-25%, AND A SOLVATED FLUID PHASE INCLUDED IN THE NETWORK-LIKE SOLID PHASE IN AN AMOUNT NOT EXCEEDING 10% BY WEIGHT OF SAID HYDROCARBON COMPOUNDS. 